The invention relates to a rotary piston internal combustion engine. In particular, the invention relates to a rotary piston internal combustion engine comprising a housing; at least one working wheel rotatable about an axis of rotation in the housing; at least one working piston provided on the working wheel for taking in and compressing air or a fuel-air mixture and for converting the gas pressure resulting from the combustion of a fuel-air mixture into mechanical energy; at least one counter wheel with at least one working piston recess; a number of first air vanes driveable in rotation for pre-compression of air or a fuel-air mixture; and at least one combustion chamber for combusting a fuel-air mixture.
Because of the rotary movement of the working piston during operation, such internal combustion engines are generally referred to as rotary piston internal combustion engines or, for short, rotary piston engines.
In this connection, it should be noted that the term axis of rotation about which the working wheel and the one or more pistons rotate during operation is not a physically embodied axle (the latter will always be referred to in the following as shaft but the physical line through the center of the rotary movement.
Internal combustion engines are divided, based on the type of movement of the working piston, i.e., that moved part which is pushed when combusting a fuel-air mixture by the resulting gas pressure, in reciprocating piston engines and rotary piston engines.
In this connection, it has been known for a long time that reciprocating piston engines require because of the translatory piston movement crank gears for conversion of the translatory movement into a rotary movement; such crank gears are highly stressed because of the forces resulting from the continuously occurring acceleration and deceleration of the pistons in particular with respect to their guides and bearings.
In contrast to this, rotary piston internal combustion engines do not have translatorily moved pistons and connecting rods, and the one or more pistons move on a circular path always in the same direction during operation so that they must not be constantly decelerated and accelerated in the opposite direction as is the case for reciprocating pistons.
The best known representative of the design of the rotary piston internal combustion engine is the Wankel engine named after its inventor. In the Wankel engine, a piston having a cross-section similar to a triangle rotates in a cylinder of a special shape. Because of sealing problems and the resulting high fuel consumption, the engine has not found acceptance despite the advantages residing in its configuration.
The German published document 29 31 943 A1 discloses a rotary piston internal combustion engine wherein two working pistons are arranged on a working wheel which is rotatably supported in a housing, wherein the working wheel is perforated in an area near the axis of rotation and is embodied as a fan wheel by means of angularly positioned stays so that the working wheel is advantageously cooled from the interior. The combustion of the fuel-air mixture is carried out in this engine in a separate combustion chamber which results in a complex configuration of the engine.
The German published document 44 17 915 A1 discloses a rotary piston internal combustion engine in which four pistons are arranged on a working wheel of which each one is embodied as a spherical piston, wherein the pistons in operation move into recesses in a counter wheel and thus form in the counter wheel a combustion chamber, wherein the pressure forces resulting from combustion act only partially in the direction of the actual circular movement of the piston so that significant forces must be taken up by the counter wheel.
The German published document 31 31 258 A1 discloses a rotary piston internal combustion engine comprising a working wheel and a compression wheel which are arranged on a common shaft. The compression wheel supports several compression pistons for compressing the fuel-air mixture which is then forced into a combustion chamber formed between the compression wheel and the blade wheel where ignition takes place. The combusted gases are moved from the combustion chamber to the working wheel where they can act on the working pistons. Intake into and exhaust from the combustion chamber are realized by a relatively complex valve control. Moreover, cooling of the working wheel and of the working pistons is problematic in this engine.
An engine which is similar to the last described engine is disclosed in the German published document DE 43 25 454 A1 in which also two piston-supporting wheels are arranged on a common shaft, with one serving for compressing air or a fuel-air mixture and the other for converting the gas pressure resulting from combustion into a rotary movement. Here, combustion is also taking place in a separate combustion chamber.
The known rotary piston internal combustion engines are relatively complex and, accordingly, require high production and maintenance expenses. Moreover, the known rotary piston internal combustion engines, despite research and development having been carried out sometimes over years, are still not optimal so that practically no rotary piston internal combustion engines can be found on the market.
It is therefore the object of the invention to provide a rotary piston internal combustion engine which has the advantages of a rotary piston engine resulting from its configuration and avoids the aforementioned disadvantages of known rotary piston internal combustion engines.
A rotary piston internal combustion engine is proposed comprising a housing; at least one working wheel rotatable in the housing about an axis of rotation; at least one working piston provided on the working wheel for compressing air or a fuel-air mixture and for converting the gas pressure resulting from the combustion of a fuel-air mixture into mechanical energy; at least one counter wheel with at least one working piston recess; several first air vanes driveable in rotation for pre-compressing air or a fuel-air mixture; and at least one combustion chamber for combusting a fuel-air mixture, wherein the at least one combustion chamber in operation is formed continuously anew between the working piston, working wheel, counter wheel, and housing, and wherein the first air vanes form, like spokes, a part of the working wheel and in operation take in the fuel-air mixture or the air through the working wheel substantially parallel to the axis of rotation of the working wheel.
The invention provides several advantages. For example, the gaseous medium, which generally is air but can however also be a fuel-air mixture, taken in through the working wheel cools the working wheel from the interior.
As a result of the perforated configuration of the working wheel with the air vanes acting as spokes, the working wheel has a high stability while having a relatively minimal weight.
The one or more working pistons provide a double function, respectively. When they move toward the counter wheel, they compress the already pre-compressed air, optionally also the already formed fuel-air mixture; after passage through the corresponding working piston recess in the counter wheel they act as a moveable wall of the combustion chamber which is pushed away by the gas pressure resulting from combustion.
The working wheel with the air vanes and one or several working pistons thus even has three functions: pre-compression, compression, work.
As a result of this multi-functionality of the components a simple configuration of the engine with minimal weight and minimal cost and high reliability is enabled. In a preferred embodiment, the output is realized by an output shaft which is arranged at the center of the working wheel whose axis of rotation is identical with the axis of rotation of the working wheel. Advantageously, the first air vanes can directly or indirectly (by a gearbox) engage the output shaft and, in this way, can transmit the mechanical energy received from the one or more pistons onto the output shaft from where it is then transmitted in a way known in the art and can be used, for example, for driving a vehicle. When the axis of rotation of the output shaft and of the working wheel coincide, this has advantages with respect to the support action and balancing.
Alternatively, it is also possible to provide an output shaft whose axis of rotation does not coincide with the axis of rotation of the working piston. The drive of the output shaft can then be realized, for example, by means of a gear rim provided on the working wheel which drives the output shaft directly or indirectly.
In an advantageous further configuration, several second air vanes that can be driven in rotation can be provided for additional pre-compression of air or of a fuel-air mixture. These second air vanes can be spoke-like parts of a gear rim and can also engage the output shaft. These spoke-shaped vanes then have a profile that, as is conventional in compression stages of a turbine, provide compression of the conveyed medium when rotated about the axis of rotation. It was found to be expedient in this connection to connect the gear rim with the second air vanes fixedly to the working wheel. When such a gear rim is provided, this gear rim with the second air vanes can be in meshing engagement with an at least partially complementary gear rim on the counter wheel. In this way, a reliable forced control of the counter wheel is realized. At the same time, when starting the engine, the working wheel can be rotated by means of the gear rim. Since the engine is actively filled in the area of the combustion chamber and has no suction function, a rotation of the working wheel caused by the starter can effect a first filling for starting the engine.
For a simple, low-maintenance, and reliable support of the working wheel and thus of the most important rotating parts of the engine, slide bearings can be provided in the housing between the inner side of the housing and the outer side of the working wheel facing the housing.
Moreover, a reservoir for receiving the gaseous medium (air or fuel-air mixture) compressed in operation by a working piston can be provided where the working piston passes the counter wheel, wherein the reservoir, for example, can be semi-cylindrical or toroidal and can be part of the housing or a separate component attached to the housing. An especially compact configuration of the engine results when the reservoir is located in the counter wheel itself, i.e., forms a part of the counter wheel. For this purpose, the counter wheel can be provided with openings and corresponding valves which are controlled in particular by spring elements or hydraulically. The gaseous medium which is compressed by a working piston upon movement toward the counter wheel is forced into a chamber formed in the counter wheel and serving as a reservoir and, after the piston has passed, is released again.
In a further preferred embodiment in which the rotary piston internal combustion engine has at least two working pistons arranged on a common working wheel, at least one intake port and one exhaust port are provided in the housing. In certain rotational positions of two neighboring working pistons, the intake port and the exhaust port are open at the same time so that it is possible to guide flushing air through the intake port into the space which is formed between the two neighboring working pistons, the housing and the working wheel. In this way, possibly still retained exhaust gases in the space are reliably pushed out. This so-called flushing air can be advantageously the gaseous medium which is taken by the first, and optionally the second, air vanes wherein the medium in this configuration is, of course, not the fuel-air mixture but air. The fuel or a fuel-air mixture is added at a later time, in particular, by means of an injection nozzle arranged behind the counter wheel.
Behind the compressor stage, which is formed by the first and second air vanes, an exhaust gas turbocharger is provided in a preferred embodiment which is capable of additionally compressing the taken-in ambient air. This exhaust gas turbocharger can be configured as a so-called soft turbocharger which generates a charge pressure which increases continuously with the engine speed.
The working pistons can be configured as solid components; preferably, they are provided with cooling means. The cooling means in one embodiment can be embodied as charging air cooling which cools the ambient air which has been taken in by the compressor stage. Another preferred embodiment comprises an active piston cooling means in which the first air vanes are essentially arranged centrally below the working pistons, wherein the working pistons have a U-shaped cooling channel. This cooling channel is flow-connected with one end with the intake side arranged in front of the compressor stage and with the opposite end with the pressure side arranged behind the compressor stage. As a result of the pressure drop along the compressor axis, an air flow through the cooling channel is formed in this configuration. In this way, a simple and efficient cooling of the working piston is ensured.
The working wheel can drive the counter wheel also by means of other drive means. This can be, for example, a drive chain which, like a control chain in conventional reciprocating piston motors, connects the gear rim of the working wheel with the complementary gear rim of the counter wheel instead of providing a direct toothed connection. Important in this connection is only the correct configuration of the transmission ratio because it must be ensured at any time that the working piston engages the working piston recess; this can be realized by the engine speed ratio required in this connection. Further features and advantages of the invention result from the dependent claims and the following description of preferred embodiments.